On Mon, 19 Mar 2007, Eric W. Biederman wrote:
> Davide Libenzi <davidel@xmailserver.org> writes:
>
> > On Mon, 19 Mar 2007, Eric W. Biederman wrote:
> >
> >> Davide Libenzi <davidel@xmailserver.org> writes:
> >>
> >> > struct signalfd_siginfo {
> >> > __u32 signo; /* si_signo */
> >> > __s32 err; /* si_errno */
> >> > __s32 code; /* si_code */
> >> > __u32 pid; /* si_pid */
> >> > __u32 uid; /* si_uid */
> >> > __s32 fd; /* si_fd */
> >> > __u32 tid; /* si_fd */
> >> > __u32 band; /* si_band */
> >> > __u32 overrun; /* si_overrun */
> >> > __u32 trapno; /* si_trapno */
> >> > __s32 status; /* si_status */
> >> > __s32 svint; /* si_int */
> >> > __u64 svptr; /* si_ptr */
> >> > __u64 utime; /* si_utime */
> >> > __u64 stime; /* si_stime */
> >> > __u64 addr; /* si_addr */
> >> > };
> >>
> >> Shouldn't we pad this to 128 bytes like we do siginfo in case there are
> >> more fields we need to include, or we need to extend the size of some
> >> field?
> >
> > Yes, I guess we can.
>
> I'm just a little paranoid about ABI's. There is always something
> that crops up. And while we can probably cope by simply having another
> version of the signalfd or whatever your syscall is, but having to do
> that at the first sign of trouble sucks. Especially since we would have
> to maintain two versions indefinitely.
Ok, I added the padding to 128 bytes to the struct.
> >> I think you want to use a struct pid *pid instead of a pointer to the
> >> task struct here. It is slightly less efficient (one more
> >> dereference) but it means that we won't pin the task struct in memory
> >> indefinitely. Pinning the task_struct like this makes for a very
> >> interesting way to get around the limits on the number of processes a
> >> user can have.
> >
> > Hmm, when the task is detached from the sighand, we get a notify, so I
> > could do a put from there. This would avoid the extra de-reference. I need
> > to verify locking though ...
>
> Ok. That sounds more efficient than playing with struct pid pointers,
> if it works.
I'm looking into this right now ...
- Davide
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